Method and device for casting steels and other ferrous compounds in ingot moulds



March 28, 1961 J, DAUSSAN 2,976,587

METHOD AND DEVICE FOR CASTING STEELS AND OTHER FERROUS COMPOUNDS IN INGOT MOULDS Flled Jan. 28, 1958 4 Sheets-Sheet 1 H. J. DAUSSAN 2,976,587 DEVICE STE AND OTHER OUS COM March 28, 1961 ELS MO ING FOR C POUND METHOD AND FERR ULDS

4 Sheets-Sheet 2 AST S IN INGOT Filed Jan. 28, 1958 wm on mmmm March 28, 1961 DAUSSAN 2,976,587

METHOD AND DEVICE FOR CASTING STEELS AND OTHER FERROUS COMPOUNDS IN INGOT MOULDS 1958 4 Sheets-Sheet 5 Filed Jan. 28.

March 28, 1961 H. J. DAUSSAN 2,976,587

METHOD AND DEVICE FOR CASTING STEELS AND OTHER FERROUS COMPOUNDS IN INGOT MOULDS 4 Sheets-Sheet 4 Filed Jan. 28, 1958 i 4 I a E nited State METHOD AND DEVICE FOR CASTING STEEL-S AND ()TgiER FERROUS COMPOUNDS IN INGOT MQULD Henri Jean Daussan, 9 Ave. Leclerc de Hauteciocque, Metz, France Filed Jan. 28, 1958, Ser. No. 711,651

Claims priority, application France Feb. 26, 1957 8 Claims. (Cl. 22-73) The present invention relates to casting ferrous compounds in ingot moulds and more particularly to the casting of effervescent and killed steels, alloy steels, and the like, these compounds being hereinafter designated broadly as metals.

It is known that, in both top casting or bottom casting, the effect of the pouring jet is responsible for many of the defects in the ingots obtained. This jet passes through the ambient air in which it remains during the entire period of top casting and for a rather long period in bottom casting. Thus, the molten metal forming this jet is oxidized and is capable of entraining a part of the ambient air. It is due to the fact that this atmospheric air surrounds the jet that the quality of the molten metal is impaired.

Further, the molten metal after leaving an open hearth electric furnace, Bessemer or Thomas converter or the like comes into contact with the atmospheric. air and is charged with oxygen, hydrogen and nitrogen. Moreover, depending on the treatment undergone by the molten metal up to the same time it reaches the ladle (killed or otherwise), said molten metal becomes the center of an internal gas formation the greater quantity of which is carbon monoxide in both killed and effervescent steels.

For instance, according to the analysis of the gaseous mixtures given off by killed or effervescent carbon steels they appear to contain:

The CO contents can however be smaller in steels alloyed with metals such as chrome, nickel, and molybdenum. It is known that within the range of pressures which may exist in the gaseous bubbles in the molten metal bath in the course of solidifying there exists:

(a) A pressure range in which the bubbles adhere to the solidification face and produce skin blisters.

(b) A lower limit to this range below which the bubbles are no longer formed.

(0) An upper limit to this range above which the bubbles become detached and no longer adhere to the wall, which explains why the inner structure of the ingot is to a large extent a function of the pressure exerted on the poured metal, the predominant pressure being the ferro-static pressure.

Attempts have been made to remove from molten steel baths the gases with which they may be charged, by elaborating the steels or by transvasing them in large chambers containing furnaces, ladles and/or ingot moulds and in which there is an extreme vacuum. These costly and complicated attempts do not, however, remove the thick molten metal layers owing to the high ferro-static pressure on these layers.

It has also been attempted to introduce into the ingotmould before and/or during casting, gases, such as CO,

2,976,537 Patented Mar. 28, 1961 F U a V argon, or nitrogen, which do not impart oxygen to the molten metal, but this is practically a useless complication especially as the protecting gases (notably CO and CO are in any case in major part given off by the molten metal bath, as is apparent from the foregoing analysis.

In the French Patent No. 1,023,443 of July 31, 1950, and in the first French Addition No. 62,755 of July 27, 1951, filed by applicant, an improved device is described for improving the casting in ingot moulds of ferrous compounds, as well as the quality of the resultant ingots, by enveloping the pouring jet and supplying the middle of the molten metal with the necessary refining substance or substances.

This device comprises an elongated sheath or tube whose length substantially corresponds to the distance between the upper face of the base of the ingot mould and the bottom of the transvasation or pouring container, this tube being composed of various metals, and notably of sheet metal which becomes destroyed upon contact with the molten metal bath.

The present invention discloses that it is possible, in utilizing the tube described in said patent and addition, to obtain a more complete improvement of the ingots, if this tube is improved in a very simple manner. Moreover, this tube can be utilized not only in top casting but also in bottom casting.

An object of the invention is therefore to provide an improved method of casting ferrous compounds in ingot moulds which permits not only effectively protecting the pouring jet from the oxidizing and diffusing effects of the atmospheric air, but which also avoids incorporation of this air into the molten metal bath by the trompe effect. This method, which employs at least one tube surrounding the jet in the manner disclosed in said patent and addition, is characterized in that it comprises, first, before pouring and at the start of pouring, obtaining an extreme vacuum in the tube and in the ingot mould and, thereafter, during the last part of the pouring and during the solidification of the ingot, effecting a suction in the tube and in the ingot mould so as to control the degasification of the poured metal by regulating the pressure of the gaseous mixture which emanates from the jet and ingot and fills the tube and ingot mould.

In the case of effervescent steel, it is possible with this improved method, to conduct the degasification in such manner that the peripheral pure iron zone of the ingot is thick and such that hydrogen is free to escape. This same advantage is obtained in killed steels, as concerns elimination of the hydrogen and thus avoids, in the cooled ingot or in the products composed thereof, dangerous internal stresses and the formation of cracks or flakes.

In the case of alloyed killed steels, it is possible to avoid to a great extent the formation of oxides.

it will be observed, furthermore, that the gases extracted from the molten metal and conducted toward the center of the molten metal bath play a useful role in the elimination of impurities (solid inclusions) up to the upper and central part of the bath. This is supplemented by utilizing in combination with the tube solid alveola floats, or floats in the form of frames which may be charged with purifying products and are protected by the tube against the destructive action of the pouring jet.

When top casting ingot moulds one by one, the stream of metal poured directly into each ingot mould is sur' rounded with said tube in each mould and the top end of the mould in which the tube is engaged is closed.

When bottom casting in such manner that several ingot moulds are filled simultaneously, the central descending jet feeding the lower castingplate is enveloped and/or the individual rising jets supplying the various ingot moulds are developed.

Another object of the invention is to provide an improved device for casting ferrous compounds according to the aforementioned process. This device comprises, at the upper end of a preferably metallic tube adapted to surround the pouring jet, a hollow connecting head provided with a branch connection to a source of suction, and a pressure gauge.

In the case of top casting and in the case of the central descending jet of a bottom casting operation, on several moulds, said head comprises an axial opening for the passage of the jet and is preferably arranged 'to adapt itself in a fluid-tight manner to the pouring container around said opening.- j

In the case of top casting and in the case of thedescending pouring jet when bottom casting with several moulds, the tube is preferably-combined with an annular cover fixed to said'tube around its upper end so as to bear against the upper face of the ingot mould surrounding this tube.

In the last two chases, the base of the tube is advantageously provided with a member adapted to ensure, prior to casting, a fluid-tight connection between the tube and the base of the ingot mould.

Further features and advantages of the invention will be apparent from the ensuing description with reference to the accompanying drawings, to which the invention is in no way restricted.

In the drawings:

i Fig. l is a vertical sectional view of a device embodying the invention, the device being in position on an ingot mould and disposed under a pouring ladle in a position corresponding to the start of the top casting;

Fig. 2 is a vertical sectional view on an enlarged scale of the upper part of the device of the invention disposed between the ingot mould and the ladle;

. Fig. 3 is a view similar to Fig. 1 at a later stage of the casting operation;

Fig. 4 is a vertical sectional view of the ingot mould, the ingot, and the remaining part of the tube, after casting at the end of the setting of an ingot cast from elfervescent steel;

Fig. 5 is a view similar to Fig. 1 for the casting of a large forge ingot of killed steel;

Fig. 6 is a view similar to Fig. 1, at the start of bottom casting, the protecting tube solely protecting the rising jet inside one of the ingot moulds this bottom casting method permits filling simultaneously, and

Fig. 7 is a view somewhat similar to Fig. 6, showing the protection of the descending central jet of a top casting operation performed on several ingot moulds.

In the embodiment shown in Figs. 1 to 4, the invention is shown to be applied to the top casting of steel A from a pouring ladle B in an ingot mould C. The ladle B is constituted by a metal container having a lateral wall 1 and a bottom 2 provided with refractory linings 3 and 4. The bottom comprises a nozzle 5 which can be closed by a stopper-rod 6; a sheath or tube composed of refractory collars 7 protects a steel rod 8 which is screwed in the stopper or plug 6 and is: controlled by a control device 9. The ladle is suspended from an overhead runway or supported on a truck so as to be brought into vertical alignment with the ingot mould C.

The ingot mould comprises a cylinder 10 which rests on a base 11 in fluid-tight manner through the medium of a sealing member 12.

The ladle B has the general shape of a body of revolution, and the ingot mould C may have any horizontal sectional shape; for example, it may be circular or be derived from a regular polygon or rectangle.

The improved device embodying the invention comprises a tube 13 of sheet metal (having a thickness of, for example, three millimetres for an inside diameter of amass? 4. 300- mm). This tube 13 terminates at its upper end in a portion which is slightlyfrusto-conical (see Fig. 2) on which is fitted a compressible sleeve 14 composed, for example, of asbestos fabric. Fitted on frusto-comcal seatings 15 and 16 on this. sleeve are an annular cover 17 and a hollow connecting head 18 respectively.

The cover 17 is adapted to bear, throught the medium of a sealing member 19, against the upper face 20 of the mould C on which it may be fixed by retractable hooks 20a which are operated from a distance owing to the provision of a stud 205 on which is engaged a cranked lever 20c, unless the weight of the cover 17 is suflicient to ensure that the connection therebetween and the mould is satisfactory and to ensure that the tube remains in position. The cover 17 is provided with a coupling 21 which permits fixing thereto, for example by means of a bayonet coupling, a flexible pipe 22 having a tap 22:: which leads to a pump, trompe or other succhamber a, and a window 24 composed of mica or other transparent material.

The connecting head 18 is in the form of a sheet metal cup or box and has preferably a circular horizontal sectional shape provided with an upper outer flange 25 and an adjoining refractory sealing member 25a (Fig. 2) in contact with which is a plate 26 attached by rivets 27 or other means to the bottom 2 of the casting ladle. Preferably, this plate is provided with locking devices which hold the head 18 in position under the plate 26 such locking devices being, for example pivotable levers 28 which engage under the flange 25 and are moved by a lever 29 It will be observed that the head 18 is divided into two superimposed chambers b and c by a sheet metal wall 30 provided with a central aperture 31 adapted to allow the free passage of the pouring jet or stream I even if the latter has increased its diameter to J (Fig. 2) owing to wear in the aperture 32 of the nozzle 5.

The aperture 31 can be closed by a register 33 connected to a control rod 34 which passes through the wall of the head 18 by way of a stuffing-box 35. The register comprises a sealing member 36 which is embedded in its lower face and is adapted to bear elastically against the raised edge or flange 37 of the aperture 31; two co-operating ramps 38 and 39 provided on the register 33 and on this raised edge, facilitate positioning the register on the latter.

The lower chamber b, which freely communicates with the interior d of the tube 13 is provided with a coupling 40, for example of the bayonet type, which permits conmeeting the chamber b to a source of suction by way of a flexible pipe 41 (Fig. 1) provided with a tap 41a. The chamber b is also provided with a pressure gauge 42.

Disposed at the base of the tube 13 (Fig. 1) isa compressible disc 43 which is destroyed by the jet of molten metal and consists, for example, of a more or less fireproofed corrugated cardboard element wound in the form of a spiral, or any other alveolar body. The purpose of this disc is to seal the connection between the tube 13 and the base 11 before casting, the tube 13 being preferably inserted at 44 in this disc. Another function of the disc is to deaden or damp the impact of the pouring jet J on the base of the mould when the pouring of the same is initiated. If desired, the disc also serves as a container of purifying, refining or addition products, the disc forming a float which floats on the molten metal bath around the tube 13 until it is totally destroyed which destruction is progressive if the disc is suitably 9 The pad or disc 43 is engaged on the lower end of the tube 13, the latter is introduced into the ingot mould, and the cover 11 is placed in position. The frust'oconical flange 15 is engaged on the sleeve 14 and deforms the latter elastically. The cover rests against the upper face of the mould to which it may be locked, if required, by retractable hooks 20a. The cover is connected to the source of suction by the pipe 22.

Further, the hollow head 18 is fixed under the ladle A. The latter is brought near to the mould and lowered onto the tube 13 whose frusto-conical upper end facilitates the fitting of the head 18 which slides along the compressible sealing member 14 of the tube 13. The latter is urged a little further into the disc 43. Under these conditions, before the stopper b is raised, the upper end of the tube 13 is connected in a fluid-tight nonrigid manner to the lower part of the ladle A and a connection is obtained between the lower end of the tube and the base 11. The pipe 41 is then connected to the coupling 40 and casting may now commence. To this end, the stopper 6 is raised by the lever 9, the molten metal falls in the form of a downwardly divergent jet or stream 3 whose impact on the base of the mould is clamped by the disc 43.

Shortly after, this jet destroys the central part of the disc 43 and the peripheral part floats at 42a on the surface of the molten metal bath A (Fig. 3), in which it is very slightly immersed (its density being much lower than that of the molten metal), whereas the tube 13 progressively melts and the steel starts to set and then to solidify at A owing to the cooling effect of the wall and the base 11. During the whole of the casting operation the pressure prevailing in the chambers a, b, c, d, are controlled in somewhat different ways according to the type of metal being cast.

Analysis will next be given of non-killed steels and killed steels which are top cast and then diflerent cases of bottom casting.

First case.N0n-killed top cast steel Non-killed (efifervescent) steel has a carbon content which varies in practice from 0.03 to 0.25% (these limits are given merely by way of example). It is known that during casting and until complete solidification of the ingot, a large amount of gas is given off whose major part is, as mentioned hereinbefore, CO accompanied by C0 the rest being formed of hydrogen, nitrogen and other atmospheric gases in smaller amounts. Their rapid evacuation, which is efliciently effected in the center of the molten metal bath according to the invention, permits improving the metal structure and disarranging to a certain extent the thickness of the peripheral pure iron part mentioned hereinbefore and binding somewhat the central segregation, which is one of the characteristics of non-killed ingots. This sheath of pure iron must have minimum thickness depending on the requirements of the subsequent rolling operations; an increase in this thickness is generally favourable unless the central segregation zone of the elements other than the iron become harmful beyond a certain concentration, which is greater as the peripheral pure iron zone in question is thicker, or the rhythm of the operations requires a more rapid setting of the ingot without impairing its quality.

Up to the present time, no process or device has permitted controlling the speed of ascension of the impurities or the thickness of the pure iron sheath in the case of non-killed steels or even the rapid and cheap elimination of gases which impair the quality of the ingot.

According to the invention, the process is carried out in the following manner:

After having rendered the chambers a, b, c, d, fluidtight by placing the cover 17 on the mould and the head 18, rigid with the ladle B, on the tube, as great a vacuum as possible is obtained in all these chambers before and at the start of casting, so as to extract the air therefrom.

This vacuum is rapidly filled owing to the gases given oif from the molten metal bath A or from the jet-I; the 'air is therefore replaced by a neutral mixture of C0, C0 N, H gases and others, and in adjusting the suction through the pipes 22 and/ or 41, there is obtained in the chamber a of the mold and in the chamber b around the jet 1 in the tube 13 desired gas pressures which are determined experimentally for a given quality of steel.

The pressure .gauges 23 and 42 indicate the pressures obtained at each instant.

By means of control taps 22a and 41a, the suction through the pipes 22 and/or 41 may be regulated in such manner that the gases issuing from the molten metal bath mix energetically and raise the impurities which are brought in by the pouring jet and are localized toward the center in the known manner by the float 42a (which could be, if necessary, larger in horizontal cross-section than shown in the drawings).

As mentioned hereinbefore, the tube 13 progressively melts as the surface of the molten metal bath A (Fig. 3) rises, but with a certain delay, so that this tube forms at its lower end a kind of hydraulic seal, the head or height h of which may be about a decimetre or more between the metal at 45 at the bottom of the tube and that situated at 46 under the float 42a. This state of affairs permits increasing the mixing of the metal by means of variations in the pressures P P prevailing at a and d, permitting pressure P to be alternately greater and then less than pressure P By means of these variations, it is possible to vary materially the level of the metal 45 situated in the end of the tube and thus considerably increase the effectiveness of the degasing, puddling or stirring.

The window 24 in the cover with the aid of viewing means fixed on the end of a tube, permits closing the nozzle 5 when the molten metal reaches the desired height in the mould.

The aperture 31 of the head is closed with the register 33 which is shifted by means of the rod 34. The head is separated from the ladle A by unlocking the locks 28, which permits removing the ladle while maintaining closed the chamber d defined by the remaining portion of the tube 13 and the chamber 0 of the hollow head remaining on the mould.

Thus it is possible to continue, if desired, the degasifi cation of the ingot in the course of the setting of the metal by means of suitable suctions created in the pipes 22 and 41 and in particular by acting on the pressures P and P as mentioned hereinbefore, during a relatively long period of time, since in the case of non-killed steel the metal may remain partially liquid for more than an hour after closing the pouring nozzle.

Thereafter, the hollow head 18 and the cover 17 are removed and the ingot has the form shown in Fig. 4, with the usual peripheral clearance 51 between the ingot and the expanded mould. In Fig. 4, A designates the peripheral part in pure iron and A the central segregated zone.

The float is generally completely destroyed and is in the form of ash and sodium silicate, if it was originally a clorrugated cardboard float impregnated with this mater1a In the case of non-killed steel, it is generally unnecessary that the float be arranged to float on the molten metal bath until the end of pouring.

The conditions of metal elaboration vary too much from one steelworks to another to permit avoiding prior trials with use of the gauges 23 and 42. However, the following are some data for a non-killed steel whose carbon content is between 0.05 and 0.08% and for ingots of 5 to 7 tons: the tube 13 could be 300 mm. in diameter and be composed of mild steel sheet 2 to 3 mm. thick whose carbon content is about the same as that of the metal to be cast. The ingot mould is filled within 1 /2 minutes to 2 minutes. The pressure in pipe 22 and/or 41 is regulated in such manner as to maintain a pressure slightly aboveatmospheric pressure, for example ,4 of an atmosphere above, except during several seconds before and after opening the pouring nozzle, during which time the suction must be increased so that the pressure in chambers a and d drops, for example, below 10 mm. of

mercury.

Second case-Top cast killed steel (Fig. 5)

This is the case of forge ingots whose weight may vary, for example, from about tons to 200 tons and more. Contrary to the preceding example, the ingot moulds C comprise a dead head portion 45, that is, a heat insulating frusto-conical or troncopyramidal 'portion and the base 11a comprises a recess 46. The latter is filled by the disc 47. The cover 17a is very much simplified, since in this embodiment there is no direct suction connection between the ingot mould and the exterior of the tube 13a. Apertures 48 formed in this tube put the interior d of the latter in communication with the chamber a in the mould.

The hollow head 18a is also simpler, the wall and the register 33 having been removed. It comprises the coupling and the pressure gauge 42.

In this case, there is no longer any substantial forma tion of gas and notably CO as occurs with non-killed steels, but it is still necessary to avoid formation of oxides above all in the case of steels strongly alloyed with precious metals, or having inclusions of impurities or occluded or dissolved gases.

The tube 13a also permits improving the structure of the metal of the ingot. This improvement is enhanced by the conjoint use of an expanding float 49 which is protected by the tube 13a so that this float, floats until the end of the pouring operation and'directs towards the center, in known manner, the impurities brought in by the pouring jet. If the jet I flowed ,freely into the mould, it would very rapidly destroy the float 49, but without the latter, the tube 13a would be powerless to moveall the impurities up to the head of the ingot.

Further, although the gases of the molten metal bat are produced in smaller quantities than in the case of non-killed steels, it is still of interest to effect a strong suction for a more or less long period of time before and after opening the pouring nozzle 5, so as to first remove the atmospheric air from the ingot mould through the apertures 48 and the end of the tube 130:.

While the molten metal rises, the gases, which exist in more or less large amounts (depending on the transvasation operations before the metal is received in the ladle) in the dissolved or occluded state in the molten metal, concentrate in the tube and are subjected to suetion at a pressure lower than atmospheric pressure, for example 10 to 20 mm. of mercury lower than the latter, until the end of the pouring operation.

It will be obvious that in the case of killed steels, the complete device of the first example could be used, which would permit varying alternately the pressures P and P prevailing in chambers a and b so as to eiiect a more thorough agitation and puddling degasification.

In any event, after having removed the ladle B, the cover 17a and the head 18a, the head of the ingot can be treated in known manner so as to avoid the central hollow, for example by the use of anti-piping powders, pads having exothermic beads and the like.

Third case.-B0tt0m cast non-killed or semi-killed steels There are two ways of carrying out the invention.

In the first way, the ascending jet in each ingot mould is protected merely bythe device shown in Fig. 6. This device and the procedure are very much simplified. The hollow head 1819 with its coupling 40 and its pressure gauge 42, is rigid with the cover 17b and is fitted with the latter on the sealing member 16b which pan be cylindrical as is the whole of the tube 13b; The lower sealing member 42!; may be annular or solid, provided that the jet J is easily able to form a passage therethrough. Before and at the start of pouring, a strong suction is created so that when the molten metal passes through the passageway 50 and the aperture 51 in the base 111) of the mould C and issues in the form of a jet J it enters a zone from which atmospheric air has been removed. At a certain level H-H above all if the metal is viscous, the jet forms a passage through the molten metal bath and emerges at 1 above said level. At this moment, the float is supposedly destroyed (the same is true for top casting). During and at the end of the pouring operation, the pressures are regulated as in the first case.

In the second way of carrying out the invention, the central jet I (Fig. 7) descending from the ladle B to the casting plate 52 is protected. The casting plate 52 feeds a series of ingot moulds filled in parallel by way of a series of passageways 53. To simplify the drawing, Fig. 7 shows only three of the ingot moulds C but their number may be greater and may even be more than 30.

The apparatus utilized comprises in this case a central tube forming a pouring well. This tube is formed preferably of a metal body 54 which rests on the casting plate 52. The inside of the tube is lined with a refractory lining 55 which is composed, for example, of superimposed collars and extends down to the various passageways 53 in the plate 52. These passageways are constituted by the juxtaposition of hollow refractory bricks; at least those of the latter which are in line with the ingot moulds having one or several apertures 56 through which the molten metal of the ascending jets I pass.

Connected to the upper end of the tube (54-55) forming the pouring well is a frusto-conical extension 57 provided for the fitting of the hollow connecting head through which the central pouring jet 3' passes. The head is provided with the coupling 40 and the pressure gauge 42.

Each ingot mould C can be equipped in the manner shown in Fig. 6 and described hereinbefore, or, as shown by the right-hand ingot mould in Fig. 7, merely with a cover 58 which has no tube, is connected to the mould in a fluid-tight manner by means of a sealing member 59 and provided with a suction coupling 21 and a pressure gauge 23.

The moulds are filled in the following manner:

After the head has been fixed under the ladle B by the device 28 and connected to the source of suction, this head is fitted on the extension 57 of the tube (54 55).

Before raising the stopper 6 hermetically closing the nozzle 5, a strong suction is created in the head 18c through the coupling 40 so that the dampness of the re fractory lining 55, the passageways 53 and their various connections and even the dampness of the dead-head portions or the coatings which may be provided in the moulds, are absorbed by the suction. This suction, which is as great as possible, also acts on the parts of the refractory linings which are but little adherent and notably at the joints of the refractory collars of the pouring well or of the hollow bricks of the passageways 53, which are generally constructed by means of cements thinned down with water.

After this cleaning and suction operation has been effected, pouring can commence. The molten metal descends at J and afterwards rises in the moulds C after passing through the passageways, the molten metal level being established at each instant in a single horizontal plane in all the moulds, which are fed in parallel.

At this moment, suction may be created, if required, in each mould through the coupling 21- of the cover 58 or through the coupling of the head of the tube if the mould is provided with a tube of the type shown in Fig. 6. The degasification is checked by means of the pressure gauge23. 1.

It will be observed that as soon as the metal has start ed to penetrate the moulds, it constitutes a hydraulic seal between the level MM in the pouring well and the level NN in the moulds, so that the suction around the jet J is substantially isolated from the moulds but continues its degasification action around the jet 1 until the level PP is reached at the end of the filling of the moulds. At this moment, the levels in the moulds and pouring well are in the same horizontal plane PP, since, owing to the stoppage of the pouring, there is no longer the dynamic effect of the jet inside the well (54-55 Fourth case.-Btt0m cast killed steel In this case, each mould may be provided, as is the mould shown on the left side of Fig. 7, with a simple thin steel plate 60 which rests on the top end of the mould without provision of a sealing member, the central pouring well having of course the tube described hereinabove.

Under the etfect of the residual hot gases given ofi? from the molten metal received in each mould, the plate 60 rises slightly to allow through the gases which may be given off by the molten metal bath, unless a slight warping of this plate under the efiect of the heat allows free passage for the gases, without allowing the outside air to enter, since the high temperature prevailing in the mould results in the residual gases having sufficient pressure to prevent this, even if they do not exist in large amounts.

Although specific embodiments of the invention have been described, many modifications and changes may be made therein without departing from the scope of the invention as defined in the appended claims.

Thus, in the case of ladles or other pouring vessels comprising several pouring nozzles for filling several moulds or a single large size mould, a tube with its associated equipment would be provided for each pouring nozzle.

Having now described my invention what I claim as new and desire to secure by Letters Patent is:

1. An improved process of casting a ferrous product in an ingot mould, said process comprising the steps of: placing in the mould a sheath capable of being destroyed progressively but with a slight delay by a molten metal bath, closing the top of the ingot mould around the sheath, creating a high vacuum within said sheath and also in the ingot mould, then pouring said product into the mould by means of a pouring jet passing inside the sheath, maintaining said high vacuum at the start of the pouring, and finally, during subsequent pouring and during the setting of the ingot, efiecting separate controlled exhaust in said sheath and in the ingot mould to degasify the molten metal by regulating separately the pressures of the gaseous mixtures emanating from said pouring jet and product, respectively, in the sheath and the mould between which the sheath which is being destroyed insures a seal due to the delay in its destruction.

2. A process according to claim 1, wherein the exhaust of the gases emanating from the molten metal is continued until the ingot has set completely,

3. An improved process of casting ferrous products in an ingot mould, said process comprising the steps of: placing in the mould a sheath capable of being destroyed progressively but with a slight delay by a molten metal bath, closing the top of the ingot mould around said sheath, creating a high vacuum within said sheath and also within the ingot mould, pouring said product into the mould by weans of a pouring jet passing inside the sheath, maintaining said high vacuum at the start of the pouring, and finally, during subsequent pouring and during the setting of the ingot, varying in opposite directions the pressures prevailing respectively within the sheath and the mould, the sheath insuring a sealing off of the interior of the sheath due to the slight delay in its destruction so as to cause, by means of variations in the level of the poured metal in the sheath, an agitating of said metal which enhances degasification.

4. A device for the casting in an ingot mould of a ferrous product contained in a pouring vessel comprising a lower nozzle for the passage of a pouring jet, said device comprising in combination: a sheath adapted to surround said pouring jet and composed of a material adapted for being destroyed with a slight delay by a molten metal bath, a hollow connecting head at the top of the sheath, the head including a branch pipe adapted for being coupled to a source of vacuum, the head further including a control pressure gage and having an upper orifice for fixing the head tightly to said pouring vessel around said nozzle, an annular cover fixed to said sheath around the upper end of the latter for resting on the top of the ingot mould around said sheath, means on said cover to connect the same to a source of vacuum whereby the pressure applied to the metal in the mould and metal in the sheath can be varied to agitate the same, and a retractable locking means for fixing said cover on the mould.

5. A device according to claim 4, wherein said cover and the hollow head are provided with apertures, by means of which they are mounted in a detachable manner on the sheath.

6. A device according to claim 5, wherein a sleeve of insulating fabric is interposed between the sheath and the apertures of the cover and the hollow head.

7. A device according to claim 6, wherein said sleeve, a corresponding portion of the sheath and the apertures of the cover and the hollow head are conical so as to facilitate their interengagement.

8. A device for the casting in an ingot mould of a ferrous product contained in a pouring vessel comprising a lower nozzle for the passage of a pouring jet, said device comprising in combination: a sheath adapted to surround said pouring jet and composed of a material adapted for being destroyed with a slight delay by a molten metal bath, a hollow connecting head at the top of the sheath, the head including a branch pipe adapted for being coupled to a source of vacuum, the head further including a control pressure gage and having an upper orifice for fixing the head tightly to said pouring vessel around said nozzle, an annular cover fixed to said sheath around the upper end of the latter for resting on the top of the ingot mould around said sheath, said cover being adapted to be connected to a source of vacuum, and a retractable locking means for fixing said cover on the mould; said device further comprising a transverse partition in said hollow head and dividing the same into two superposed chambers, said transverse partition having an aperture for the passage of the jet and comprising a register movably mounted in the head to close the latter said aperture for maintaining suction in the sheath, and a coupling adapted for connection to a source of vacuum on the lower chamber into which the sheath opens.

References Cited in the file of this patent UNITED STATES PATENTS 917,257 Critchlow Apr, 6, 1909 1,568,854 Larner Jan. 5, 1926 1,679,582 Nelson Aug. 7, 1928 1,759,269 Morrison May 20, 1930 2,087,824 Tully July 20, 1937 2,117,114 Hazey' May 10, 1938 2,253,421 De Mare Apr. 19, 1941 2,734,241 Southern Feb. 14, 1956 FOREIGN PATENTS 2,831 Great Britain Nov. 14, 1864 62,755 France Feb. 9, 1955 212,697 Great Britain Mar. 20, 1924 523,595 Canada Apr. 10, 1956 

